The Aalto-1 nanosatellite navigation subsystem: Development results and planned operations

Aalto-1, the first satellite built in Finland, is due to be launched during the first half of 2016. The 4 kg satellite has been designed and built at Aalto University and is based on the CubeSat standard. The satellite carries three payloads: a spectral imager (AaSI) by the Technical Research Center of Finland, a radiation monitor (RADMON) by the University of Turku, and an electrostatic plasma brake (EPB) by the Finnish Meteorological Institute. The payloads require accurate position information to support their scientific missions. CubeSat missions usually plan operations and process scientific data based on two-line element (TLE) orbital parameter sets made available by the United States Air Force. However, the TLE sets may have errors up to several km at epoch, and it was decided that the satellite will be equipped with an independent navigation subsystem capable of more accurate positioning. This paper describes the development results and planned operations of the GPS-based navigation subsystem of Aalto-1. The navigation subsystem has been designed and built using commercial off-the-shelf (COTS) components. The navigation subsystem has gone through an extensive qualification process both individually and as a part of Aalto-1 satellite-level qualification. The orbital navigation capability of the receiver has been functionally tested with a GPS signal simulator. Navigation system operations are designed around the scientific mission of the satellite. Analysis tools have been developed for the navigation data that can determine the satellite state vector within 5 m and 0.05 m/s accuracy. Development results and lessons learned are discussed.